Chapter 2 - The Open Systems Interconnection Specifications (OSI) Flashcards
What is the OSI Model?
The OSI Model is a conceptual guideline that provides a framework for creating and implementing networking standards, devices, and internetworking schemes.
How many layers are in the OSI Model? List each one.
There are 7 layers in the OSI model?
Physical, Data Link, Network, Transport, Session, Presentation, Application
What is Layer 5?
Session Layer
What is Layer 1?
Physical Layer
What is Layer 7?
Application Layer
What is Layer 4?
Transport Layer
What is Layer 2?
Data Link Layer
What is Layer 3?
Network Layer
What is Layer 6?
Presentation Layer
What is the Role of the Application Layer?
Provide a user interface
What is the Role of the Presentation Layer?
Presents data; Handles processing such as encryption
What is the Role of the Session Layer ?
Keeps different application’s data separate
What is the Role of the Transport Layer?
Provide reliable or unreliable delivery; Performs error correction before transmit
What is the Role of the Network Layer?
Provides logical addressing, which routers use for path determination
What is the Role of the Data Link Layer?
Combines packets into bytes and bytes into frames; Provides access to media using MAC address; Performs error detection, not correction
What is the Role of the Physical Layer?
Moves bits between devices; Specifies voltage, wire speed, and pin-out of cables
What are the layers in the UPPER LAYERS group of the OSI and what does this group define?
The UPPER LAYERS are the APPLICATION, PRESENTATION, and SESSION LAYERS, which defines the rules of how the applications working within the host machine communicate with each other as well as end users.
What are the layers in the LOWER LAYERS group of the OSI and what does this group define?
The LOWER LAYERS are the TRANSPORT, NETWORK, DATA LINK, and PHYSICAL LAYERS, which defines how the actual data is transmitted from end to end
What are the functions of the Physical Layer?
Physical Topology; Physically, mechanically and/or electronically connect network devices; Breaks frames into binary bits; Defines the network media used
What are the functions of the Data Link Layer?
Framing; Breaks data packet into frames, Manages Hardware (MAC) addresses, Defines the logical topology of the network based on IEEE 802.x standards; provides error and flow control
What are the functions of the Network Layer?
Routing; Break segmented data into packets and sequences them; Assigns Logical addresses to packets; Routes packets
What are the functions of the Transport Layer?
End-to-end connection; Packages data into segments; Provides flow control; Performs end-to-end transport of data
What are the functions of the Session Layer?
Dialog control; Assumes a reliable virtual connection; Establishing, maintaining, synchronizing and terminating connections; Port numbers are assigned and maintained
What are the functions of the Presentation Layer?
Data encryption, compression, decompression and translation services; Reformat or translate between different character sets; Provides support for recovery
What are the functions of the Application Layer?
File, print, message, database, and application services; Takes data from applications; Ensures all necessary resources are available; initalizes services and the network for data transmission
What are the two sublayers of the Data Link Layer?
Media Access Control (MAC) Sublayer &
Logical Link Control (LLC) Sublayer
What is the function of the Media Access Control Sublayer?
The MAC sublayer is responsible for physical addressing and determining the appropriate time to place data on the network.
What is the function of the Logical Link Control Sublayer?
The LLC sublayer is responsible primarily for the multiplexing of Network layer protocols
Hubs and Repeaters operate at what layer?
All networking devices operate at the physical layer because they have physical connectivity, but, hubs and repeaters only operate at the PHYSICAL LAYER because they only see bits. Cable connectors, Transceivers, and NICs also function at this layer.
Switches and Bridges operate at what layer?
Switches and Bridges are considered layer 2, DATA LINK Layer devices because the utilize MAC addressing
Routers operate at what layer?
Routers operate at layer 3, the NETWORK LAYER because they utilize logical (IP) addressing.
What they two types of packets used at the Network Layer?
Data Packets and Route-Update Packets
What are Data Packets?
Data packets are used to transport user data through the internetwork. Routed protocols, such as IP and IPv6 support the data traffic
What are Route-Update Packets?
Route-Update Packets utilize routing protocols such as RIP, RIPv2, OSPF, and EIGRP to help build and maintain routing tables on each router within an internetwork
